The present invention relates generally to solid state microwave integrated circuits, and more particularly, to apparatus and methods for installing and removing insulator-encapsulated contacts employed in such microwave integrated circuits.
Solid state microwave integrated circuits typically employ insulator-encapsulated contacts, such as 50 ohm feedthrough contacts. Should a contact need to be replaced due to damage or hermeticity failure, the conventional process calls for disassembly of the unit, i.e., removal of all internal electronics such as substrates, mixers, ribbons, wire bonds, and other components. Some substrates are mounted to a housing on carriers, others are bonded to the housing, in which case bonding removal is necessary. The bare housing is then placed on a hot plate and heated to a temperature of 250.degree. C., which is around 60.degree. C. higher than the reflow, or melting temperature of 186.degree. C. The contact in question is replaced, the housing cleaned, substrates reinstalled, or rebonded, and gap welding is done before the unit is ready for leak test.
The disadvantages of this conventional process include the following. It is time-consuming and labor intensive. It takes a minimum of 4 hours from start to finish, and in some cases longer, depending upon the complexity of the circuit. Many times multiple operators are involved before the process is completed. The conventional process introduces unnecessary thermal shock to solder joints. Most MICs have more than one contact, and heating the entire assembly causes all solder joints to reflow, regardless of whether it is necessary, therefore increasing the likelihood of reflowing an otherwise good solder joint. Finally, should a device fail a post-rework hermeticity test, the replacement process must be repeated.
Therefore it is an objective of the present invention to provide for improved apparatus and methods for installing and removing insulator-encapsulated contacts, such as 50 ohm feedthrough contacts, and the like, employed in such microwave integrated circuits.